Updated Phase Diagram Research Articles

Pseudogap in Sr2−xLaxIrO4: Gor'kov-Teitel'baum thermal activation model

Recently, Hall effect measurements are done on Lanthanum doped Strontium Iridate Sr2−xLaxIrO4 which is 5d analogue of cuprates [1]. Hall effect measurements show that the effective carrier density nH exhibits a crossover from nH∼x to nH∼1+x near x≃0.16. This is very similar to that found in cuprates around p≃0.19. It is proposed that a pseudogap (PG) state in Sr2−xLaxIrO4 exists and is ending at x≃0.16[1]. However, PG boundary (in doping-temperature phase diagram) remains unknown. In this work, we apply a very successfull the Gor'kov-Teitel'baum Thermal Activation (GTTA) model to Sr2−xLaxIrO4 and obtain its PG phase boundary and draw an updated phase diagram. Our results agree with previously known signatures of PG phase in this system [2–4]. Using results from GTTA model we also obtain the evolution of “Fermi arcs” in this system as a function temperature for doping concentration x≃0.08 which are in qualitative agreement with the reported results.

A refined phase diagram of the GeTe-Bi2Te3 system

Updated phase diagram of the GeTe–Bi2Te3 system was constructed using differential thermal, X-ray diffraction analysis and scanning electron microscopy (SEM) results of alloys synthesized with specially developed technology. The refined version significantly differs from those reported so far. The presented phase diagram reflects six ternary compounds: Ge4Bi2Te7, Ge3Bi2Te6, Ge2Bi2Te5, GeBi2Te4, GeBi4Te7, and GeBi6Te10. The study determined that the first two compounds are formed as a result of solid-state reactions at temperatures of 750–800 K, and the latter four are formed as a result of peritectic reactions at 863, 854, 848, and 843 K, respectively. Wide homogeneity regions based on the initial binary compounds were also found. These regions reach 10 mol% at room temperature. The coordinates of eutectic point are 83 mol% Bi2Te3 and 838 K. It crystallises at 838 К. It was found that all the identified ternary compounds crystallise in a tetradymite-like layered structure. Ge4Bi2Te7, Ge3Bi2Te6, Ge2Bi2Te5, and GeBi2Te4 compounds belong to the nGeTe·Bi2Te3 homologous series. Their crystal lattices are formed by the insertion of GeTe bilayers into the quintuple Bi2Te3 layers. GeBi4Te7 and GeBi6Te10 compounds are representatives of the GeTe·mBi2Te3homologous series and have a mixed-layer structure. The parameters of the crystal lattices of the compounds were determined by the Rietveld method based on their powder diffraction data.

The updated basti stellar evolution models and isochrones – III. White dwarfs

ABSTRACT We present new cooling models for carbon–oxygen white dwarfs (WDs) with both H- and He-atmospheres, covering the whole relevant mass range, to extend our updated basti (a Bag of Stellar Tracks and Isochrones) stellar evolution archive. They have been computed using core chemical stratifications obtained from new progenitor calculations, adopting a semi-empirical initial–final mass relation. The physics inputs have been updated compared to our previous basti calculations: 22Ne diffusion in the core is now included, together with an updated CO phase diagram, and updated electron conduction opacities. We have calculated models with various different neon abundances in the core, suitable to study WDs in populations with metallicities ranging from supersolar to metal poor, and have performed various tests/comparisons of the chemical stratification and cooling times of our models. Two complete sets of calculations are provided, for two different choices of the electron conduction opacities, to reflect the current uncertainty in the evaluation of the electron thermal conductivity in the transition regime between moderate and strong degeneracy, crucial for the H- and He-envelopes. We have also made a first, preliminary estimate of the effect – that turns out to be generally small – of Fe sedimentation on the cooling times of WD models, following recent calculations of the phase diagrams of carbon–oxygen-iron mixtures. We make publicly available the evolutionary tracks from both sets of calculations, including cooling times and magnitudes in the Johnson-Cousins, Sloan, Pan-STARSS, GALEX, Gaia-DR2, Gaia-eDR3, HST-ACS, HST-WFC3, and JWST photometric systems.

On the crystal structures of lithium thiocyanate monohydrate LiSCN [formula omitted] 1 H2O and the phase diagram LiSCN – H2O

Hydration of anhydrous LiSCN by stoichiometric amounts of water vapor leads to the formation of LiSCN ⋅ 1 H2O. At room temperature, LiSCN ⋅ 1 H2O crystallizes in the monoclinic space group C2/m with a = 15.0271(3) Å, b = 7.5974(1) Å, c = 6.7070(1) Å, β = 96.147(6) ° and V = 761.32(2) ų (α-phase). At 49 °C, the material transforms into a high temperature β-phase with the orthorhombic space group Pnam and a = 13.2258(2) Å, b = 7.0619(9) Å, c = 8.1663(1) Å and V = 762.72(2) ų. Structural and thermodynamic investigations were conducted using infrared (IR) spectroscopy, ex situ and in situ X-ray powder diffraction (XRPD) while varying temperature or water partial pressure pH2O, differential scanning calorimetry (DSC) and direct measurements of equilibrium pH2O. The results indicate that LiSCN ⋅ 1 H2O is a special case when compared to LiSCN ⋅n H2O (n = 0 or 2), both regarding crystal structure and hydration thermodynamics. These results are combined with literature date into an updated phase diagram of the LiSCN – H2O system, showing a detailed picture of the phase formation behavior of the LiSCN ⋅n H2O hydrates.

An Updated Phase Diagram of the SnTe-Sb2Te3 System and the Crystal Structure of the New Compound SnSb4Te7

An Updated Phase Diagram of the SnTe-Sb2Te3 System and the Crystal Structure of the New Compound SnSb4Te7

Diverse densest binary sphere packings and phase diagram

We revisit the densest binary sphere packings (DBSPs) under periodic boundary conditions and present an updated phase diagram, including newly found 12 putative densest structures over the x-α plane, where x is the relative concentration and α is the radius ratio of the small and large spheres. To efficiently explore the DBSPs, we develop an unbiased random search approach based on both the piling-up method to generate initial structures in an unbiased way and the iterative balance method to optimize the volume of a unit cell while keeping the overlap of hard spheres minimized. With those two methods, we have discovered 12 putative DBSPs and thereby the phase diagram is updated, while our results are consistent with those of a previous study [Hopkins et al., Phys. Rev. E 85, 021130 (2012)]PLEEE81539-375510.1103/PhysRevE.85.021130 with a small correction for the case of 12 or fewer spheres in the unit cell. Five of the discovered 12 DBSPs are identified in the small radius range of 0.42≤α≤0.50, where several structures are competitive to each other with respect to packing fraction. Through the exhaustive search, diverse dense packings are discovered and, accordingly, we find that packing structures achieve high packing fractions by introducing distortion and/or combining a few local dense structural units. Furthermore, we investigate the correspondence of the DBSPs with crystals based on the space group. The result shows that many structural units in real crystals, e.g., LaH_{10} and SrGe_{2-δ} being high-pressure phases, can be understood as DBSPs. The correspondence implies that the densest sphere packings can be used effectively as structural prototypes for searching complex crystal structures, especially for high-pressure phases.

Materials preparation, single-crystal growth, and the phase diagram of the cuprate high-temperature superconductor La1.6−xNd0.4SrxCuO4

One branch of the La-214 family of cuprate superconductors, La1.6-xNd0.4SrxCuO4 (Nd-LSCO), has been of significant and sustained interest, in large part because it displays the full complexity of the phase diagram for canonical hole-doped, high Tc superconductivity, while also displaying relatively low superconducting critical temperatures. The low superconducting Tc's imply that experimentally accessible magnetic fields can suppress the superconductivity to zero temperature. In particular, this has enabled various transport and thermodynamic studies of the T = 0 ground state in Nd-LSCO, free of superconductivity, across the critical doping p* = 0.23 where the pseudogap phase ends. The strong dependence of its superconducting properties on its crystal symmetry has itself motivated careful studies of the Nd-LSCO structural phase diagram. This paper provides a systematic study and summary of the materials preparation and characterization of both single crystal and polycrystalline samples of Nd-LSCO. Single-phase polycrystalline samples with x spanning the range from 0.01 to 0.40 have been synthesized, and large single crystals of Nd-LSCO for select x across the region (0.07, 0.12, 0.17, 0.19, 0.225, 0.24, and 0.26) were grown by the optical floating zone method. Systematic neutron and X-ray diffraction studies on these samples were performed at both low and room temperatures, 10 K and 300 K, respectively. These studies allowed us to follow the various structural phase transitions and propose an updated structural phase diagram for Nd-LSCO. In particular, we found that the low-temperature tetragonal (LTT) phase ends at a critical doping pLTT = 0.255(5), clearly separated from p*.

Inversion of quartz solid solutions at cryogenic temperatures

AbstractQuartz solid solution crystals of six different compositions were obtained from crystallization of glass powders belonging to the Li2O–Al2O3‐SiO2 (LAS) system. They were analyzed in situ by laboratory‐based X‐ray diffraction down to cryogenic temperatures (−190°C). Temperature‐resolved analysis of their lattice parameters allowed determination of the critical inversion temperature Tc in these materials, marking the displacive phase transition from a high‐quartz‐ to a low‐quartz‐like lattice. Integrating available data from other literature sources, an updated phase diagram for the occurrence of high and low quartz solid solution phases is provided for the LAS system; these data are expected to support future development of functional materials relying on these crystalline phases.

High Pressure Hydrocarbons Revisited: From van der Waals Compounds to Diamond

Methane and other hydrocarbons are major components of the mantle regions of icy planets. Several recent computational studies have investigated the high-pressure behaviour of specific hydrocarbons. To develop a global picture of hydrocarbon stability, to identify relevant decomposition reactions, and probe eventual formation of diamond, a complete study of all hydrocarbons is needed. Using density functional theory calculations we survey here all known C-H crystal structures augmented by targeted crystal structure searches to build hydrocarbon phase diagrams in the ground state and at elevated temperatures. We find that an updated pressure-temperature phase diagram for methane is dominated at intermediate pressures by CH 4 :H 2 van der Waals inclusion compounds. We discuss the P-T phase diagram for CH and CH 2 (i.e., polystyrene and polyethylene) to illustrate that diamond formation conditions are strongly composition dependent. Finally, crystal structure searches uncover a new CH 4 (H 2 ) 2 van der Waals compound, the most hydrogen-rich hydrocarbon, stable between 170 and 220 GPa.

Effect of synthesis route on structure and dielectric properties of (1-x)BiFeO3-xBaTiO3 solid solutions and its phase diagram

We present here a comparative study of structure, surface morphology, composition analysis, and dielectric properties of (1-x)BiFeO3-xBaTiO3 (BF-xBT) solid solutions, synthesized by two different solid state reaction routes reported in the literature. The results of structural and dielectric studies suggest that BF-xBT ceramics synthesized using BaTiO3, Bi2O3, and Fe2O3 (method-I) as initial ingredients are not monophasic for 0.50 < x < 0.80. In this composition range, we observe the phase coexistence of tetragonal and rhombohedral/pseudocubic phases. The ferroelectric Curie temperature (TC ∼ 400 K) of this tetragonal phase corresponds to the TC of BaTiO3. Composition analysis of these ceramics also confirms the presence of BaTiO3-rich phase. These observations suggest that BaTiO3 does not react completely with Bi2O3 and Fe2O3 when synthesized by method-I. In marked contrast, the BF-xBT solid solutions synthesized by method-II using Bi2O3, Fe2O3, BaCO3, and TiO2 as initial ingredients are compositionally homogeneous and single phase in the entire composition range (0 < x ≤ 1). The average atomic percentage of Bi, Fe, Ba, and Ti for BF-xBT ceramics synthesized by method-II, as obtained from energy dispersive x-ray spectroscopy, is close to the nominal composition within ±2%. Structural and dielectric studies do not reveal any signature of the coexistence of phases in these samples. Using the results of structural and dielectric studies, we also present a new and updated phase diagram of BF-xBT synthesized by method-II.

Nitrogen Transfer between Solid Phases in the System Mn‐N Detected via in situ Neutron Diffraction

The thermochemical properties of θ‐Mn6N5+x and ζ‐Mn2N1–w were investigated by thermal analysis in inert and oxidizing atmospheres. The obtained phase transformation temperatures were used to design an in situ neutron diffraction experiment on the reaction of α‐Mn and flowing NH3. During this in situ experiment, initially a nitrogen‐poor anti‐perovskite type phase ε‐Mn4Ny [0.70(3) ≤ y ≤ 0.93(3)] was formed, indicating the lowest required nitridation potential necessary for formation of this phase within the binary manganese nitrides. At slightly higher temperatures the γ‐ and β‐type superstructured polymorphs of ζ‐Mn2N1–w were observed. In the same temperature region the formation of η‐Mn3N2 [up to 26(2) wt %] at ambient pressure conditions was noticed. For the first time, a direct evidence for the high‐temperature transformation of η‐Mn3N2 was obtained. At 928 K the nuclear and magnetic superstructures simultaneously collapse and a cubic MnNx phase [0.56(6) ≤ x ≤ 0.70(3)] with defect rock salt structure was generated. Clear indications for the preferred transfer of N between the different above mentioned solid state nitride phases rather than direct release to the surrounding atmosphere during temperature increase were achieved from the compositions of the coexisting phases. An updated phase diagram is suggested.

Collective magnetic excitations of C4 -symmetric magnetic states in iron-based superconductors

We study the collective magnetic excitations of the recently discovered $C_{4}$ symmetric spin-density wave states of iron-based superconductors with particular emphasis on their orbital character based on an itinerant multiorbital approach. This is important since the $C_{4}$ symmetric spin-density wave states exist only at moderate interaction strengths where damping effects from a coupling to the continuum of particle-hole excitations strongly modifies the shape of the excitation spectra compared to predictions based on a local moment picture. We uncover a distinct orbital polarization inherent to magnetic excitations in $C_{4}$ symmetric states, which provide a route to identify the different commensurate magnetic states appearing in the continuously updated phase diagram of the iron-pnictide family.

Experimental Study and Thermodynamic Modeling of Phase Equilibria in BaO-Fe<sub>2</sub>O<sub>3</sub> System

This paper presents the results of the synthesis of compounds of BaO-Fe2O3 system and the results of the study of nature and the melting temperatures of the resulting compounds. Based on the analysis of published data, as well as the results of our studies the systematization of information on the BaO-Fe2O3 system was conducted and an updated phase diagram of this system was proposed.

Phase diagram and magnetization structures of spin-32 bond-alternating Ising chains with single-ion anisotropy

Abstract By the infinite time-evolving block decimation (iTEBD) algorithm, the magnetization process of the spin- 3 2 bond-alternating Ising chain with single-ion anisotropy (D) is investigated. Magnetization plateaus including detailed magnetization structures of three different cases are uncovered, and three rich ground-state phase diagrams are explicitly determined. Especially, for the uniform antiferromagnetic case, a phase transition line at D=J, which divides the Mz=0 ( M z = 1 2 ) plateau into two phases, are detected by the magnetization structure and the ground-state energy, and a updated phase diagram is proposed. Such a transition line was not recognized by the average magnetization previously. A same transition line (D=J) is also detected in the phase diagram of the antiferromagnetic-ferromagnetic alternating case. Magnetization plateaus are found to be easily induced for the classical Ising systems without quantum fluctuations, and the single-ion anisotropy plays a key role in the formation of M z = 1 2 and 1 plateaus in the present model.

Supplemental Literature Review of Binary Phase Diagrams: B-La, B-Zn, Bi-La, Bi-Ti, Cd-Pr, Ce-Ga, Cu-Na, Ge-Ta, Ge-Y, H-Zr, Na-Si, and Pb-Sc

Binary Alloy Phase Diagrams, 2nd edition, a comprehensive collection of alloy phase diagrams for 2159 binary systems, was published in 1990 (T.B. Massalski, H. Okamoto, P.R. Subramanian, and L. Kacprzak., ASM International, Materials Park, OH [Massalski2]). This review intends to provide more recent information on the binary phase diagrams for the B-La, B-Zn, Bi-La, Bi-Ti, CdPr, Ce-Ga, Cu-Na, Ge-Ta, Ge-Y, H-Zr, Na-Si, and Pb-Sc systems that have become available after 1990. The criteria for selecting such information for inclusion in this review are (1) systems for which no phase diagram was given in [Massalski2], (2) complete diagrams that are substantially different from the earlier version, and (3) partial diagrams that alter or clarify the earlier version. Thermodynamic consistency of the new phase diagrams was checked based on phase rules and the diagrams were modified if necessary. However, each updated phase diagram has not gone through the ordinary evaluation process. Accordingly, a newer phase diagram is not always a better diagram, especially when there is too little published data on a system. For convenience, reaction tables and crystal structure data have been added when new information was available.

Supplemental Literature Review of Binary Phase Diagrams: Al-P, B-Ga, B-Nd, Ba-Ga, Bi-Cs, Ca-Ga, Cd-Gd, Cr-Mo, Gd-Ni, Ni-Pb, Ni-Sc, and Sc-Sn

Binary Alloy Phase Diagrams, 2nd edition, a comprehensive collection of alloy phase diagrams for 2159 binary systems, was published in 1990 (T.B. Massalski, H. Okamoto, P.R. Subramanian, and L. Kacprzak., ASM International, Materials Park, OH [Massalski2]). This review intends to provide more recent information on the binary phase diagrams for the Al-P, B-Ga, B-Nd, Ba-Ga, Bi-Cs, Ca-Ga, Cd-Gd, Cr-Mo, Gd-Ni, Ni-Pb, Ni-Sc, and Sc-Sn systems that have become available after 1990. The criteria for selecting such information for inclusion in this review are (1) systems for which no phase diagram was given in [Massalski2], (2) complete diagrams that are substantially different from the earlier version, and (3) partial diagrams that alter or clarify the earlier version. Thermodynamic consistency of the new phase diagrams was checked based on phase rules and the diagramsweremodified if necessary. However, each updated phase diagram has not gone through the ordinary evaluation process. Accordingly, a newer phase diagram is not always a better diagram, especially when there is too little published data on a system. For convenience, reaction tables and crystal structure data have been added when new information was available.

Supplemental Literature Review of Binary Phase Diagrams: Bi-Ga, Bi-Y, Ca-H, Cd-Fe, Cd-Mn, Cr-La, Ge-Ru, H-Li, Mn-Sr, Ni-Sr, Sm-Sn, and Sr-Ti

Binary Alloy Phase Diagrams, 2nd edition, a comprehensive collection of alloy phase diagrams for 2159 binary systems, was published in 1990 (T.B. Massalski, H. Okamoto, P.R. Subramanian, and L. Kacprzak., ASM International, Materials Park, OH [Massalski2]). This review intends to provide more recent information on the binary phase diagrams for the Bi-Ga, Bi-Y, Ca-H, Cd-Fe, Cd-Mn, Cr-La, Ge-Ru, H-Li, Mn-Sr, Ni-Sr, Sm-Sn, and Sr-Ti systems that have become available after 1990. The criteria for selecting such information for inclusion in this review are (1) systems for which no phase diagram was given in [Massalski2], (2) complete diagrams that are substantially different from the earlier version, and (3) partial diagrams that alter or clarify the earlier version. Thermodynamic consistency of the new phase diagrams was checked based on phase rules and the diagrams were modified if necessary. However, each updated phase diagram has not gone through the ordinary evaluation process. Accordingly, a newer phase diagram is not always a better diagram, especially when there is too little published data on a system. For convenience, reaction tables and crystal structure data have been added when new information was available.

Updating the phase diagram of the archetypal frustrated magnetGd3Ga5O12

The applied magnetic field and temperature phase diagram of the archetypal frustrated magnet, ${\mathrm{Gd}}_{3}{\mathrm{Ga}}_{5}{\mathrm{O}}_{12}$, has been reinvestigated using single-crystal magnetometry and polarized neutron diffraction. The updated phase diagram is substantially more complicated than previously reported and can be understood in terms of competing interactions with loops of spins, trimers, and decagons, in addition to competition and interplay between antiferromagnetic, incommensurate, and ferromagnetic order. Several additional distinct phase boundaries are presented. The phase diagram centers around a multiphase convergence to a single point at 0.9 T and $\ensuremath{\sim}0.35$ K, below which, in temperature, a very narrow magnetically disordered region exists. These data illustrate the richness and diversity that arise from frustrated exchange on the three-dimensional hyperkagome lattice.

Composition-driven structural phase transitions in rare-earth-doped BiFeO3 ceramics: a review.

Bismuth ferrite suffers from high leakage currents and the presence of a complex incommensurate spin cycloidal magnetic ordering, which has limited its commercial viability and has led researchers to investigate the functionality of doped BiFeO3 ceramics. In particular, the substitution of rare earths onto the Bi(3+) site of the perovskite lattice have been shown to lead to improved functional properties, including lower leakage currents and the suppression of the magnetic spin cycloid. There is particular interest in materials with compositions close to structural morphotropic phase boundaries, because these may lead to materials with enhanced electronic and magnetic properties analogous to the highly relevant PbZrO3- PbTiO3 solid solution. However, many contradictory crystal structures and physical behaviors are reported within the literature. To understand the structure-property relationships in these materials, it is vital that we first unravel the complex structural phase diagrams. We report here a comprehensive review of structural phase transitions in rare-earth-doped bismuth ferrite ceramics across the entire lanthanide series. We attempt to rationalize the literature in terms of the perovskite tool kit and propose an updated phase diagram based on an interpretation of the literature.

Supplemental Literature Review of Binary Phase Diagrams: Al-Mg, Bi-Sr, Ce-Cu, Co-Nd, Cu-Nd, Dy-Pb, Fe-Nb, Nd-Pb, Pb-Pr, Pb-Tb, Pd-Sb, and Si-W

Binary Alloy Phase Diagrams, 2nd edition, a comprehensive collection of alloy phase diagrams for 2159 binary systems, was published in 1990 (T.B. Massalski, H. Okamoto, P.R. Subramanian, and L. Kacprzak., ASM International, Materials Park, OH [Massalski2]). This review intends to provide more recent information on the binary phase diagrams for the Al-Mg, Bi-Sr, Ce-Cu, Co-Nd, Cu-Nd, Dy-Pb, Fe-Nb, Nd-Pb, Pb-Pr, Pb-Tb, Pd-Sb, and SiW systems that have become available after 1990. The criteria for selecting such information for inclusion in this review are (1) systems for which no phase diagram was given in [Massalski2], (2) complete diagrams that are substantially different from the earlier version, and (3) partial diagrams that alter or clarify the earlier version. Thermodynamic consistency of the new phase diagrams was checked based on phase rules and the diagrams were modified if necessary. However, each updated phase diagram has not gone through the ordinary evaluation process. Accordingly, a newer phase diagram is not always a better diagram, especially when there is too little published data on a system. For convenience, reaction tables and crystal structure data have been added when new information was available.